A communication system is formed, at a minimum, of a base station and a mobile station, which are interconnected by way of a communication channel. Information to be communicated by the base station (also referred to as cell site) to the mobile station is transmitted via the communication channel to the mobile station. A wide variety of different types of communication systems have been developed and are regularly utilized to effectuate communication of information between base stations and mobile stations.
A wireless communication system, is an example of a communication system, which has been made possible due to advancements in communication technologies. Various standards have been promulgated relating to various types of wireless communication systems, and various types of wireless, as well as other, communication systems have been constructed, corresponding to such standards. The IS-95 and IS-2000 interim standards, promulgated by the EIA/TIA, are exemplary of standards which pertain to a wireless communication system, utilizing code division multiple access (CDMA) communication techniques.
Enhanced 3rd Generation CDMA systems are currently being developed to address high speed Internet packet data services. Examples of such systems, which are the result of an evolution of IS-95 and IS2000, are 1XEV-DO (TIA/EIA/IS-856) and 1XEV-DV standards. These systems utilize both CDMA and some type of time division multiplexing communication techniques.
In an effort to port the Internet to the wireless communication system, 1XEV-DO and 1XEV-DV systems use a fat data pipe concept, which is shared among a number of users (mobile stations). The fat pipe, called the shared supplemental channel, is de-multiplexed into several code channels according to the usual CDMA access techniques. In the current proposal for 1XEV-DV, for example, the pipe is actually transmitted on 14 or 15 Walsh codes of length 16.
In high data rate systems, it is assumed that low mobility prevails and the use of soft handoff is not needed. Also, use of soft handoff would reduce the data rate capacity of the system. Therefore, a fast cell site selection is performed in the network, aided by measurements made at the mobile station. However, the mobile station can only assist the BS by sending information on the reverse link. Because of impairments on the reverse link, the BS may actually select a less then preferred cell site. instead of the preferred target cell site
In the high data rate, the shared supplemental channel is shared among a number of mobile stations in accordance with CDMA and TDMA communication techniques. The base station has an admission control algorithm such that the base station decides 1) when to transmit data packets to a particular mobile station; 2) the modulation type and coding rate; 3) the Walsh codes (among the 14 or 15 available) that will be assigned; and 4) the cell site that will transmit the data packets.
The BS simultaneously transmits the data packet, intended for the mobile station, on the supplemental channel and a signaling frame on the dedicated channel. This signaling frame provides the mobile station information such as 1) whether a data packet was sent to that MS; 2) the modulation type and coding rate used; 3) the Walsh codes; and 4) which cell site is transmitting on shared supplemental channel. Upon reception of a signaling frame, the mobile station decodes the dedicated channel and determines if there was a data packet for it on the shared supplemental channel. Thus, the mobile station is expected to buffer the received shared supplemental channel information in order to be able, after the fact, demodulate and decode the share supplemental channel. Generally, the dedicated channel and all the supplemental channels are de-spread to retrieve necessary information and all the expanded information is stored is a buffer. Generally, the buffer size required depends on the number of fingers needed, the number of Walsh channels, the sampling rate, etc. Since the mobile station must de-spread all the Walsh channels to determine if a data packet is transmitted for that MS, a large buffer size is needed, even if only one Walsh channel may apply.
Therefore, it would be useful if method and apparatus was provided to manage the buffering and processing of signals that would require less storage space and processing time.